Power unit

ABSTRACT

An improved power unit for driving vegetable cutting attachments comprises a housing, a motor mounted within the housing, an attachment supporting hub mounted on the front of the housing and a drive for connecting the motor to a shaft extension of the attachment. The drive includes a drive sleeve mounted for rotation and radial displacement in the hub, a sprocket attached to the rear of the sleeve and a resilient bracket for universally and rotatably supporting the rear end of the sleeve. The shaft extension of the vegetable cutter extends a relatively short distance into the front end of the drive sleeve to provide, in combination with the radial displacement of the sleeve and with the resilient rear bracket, a universal driving connection therebetween. A tensioner is provided to tension a chain connecting the sprocket attached to the sleeve and a sprocket on a motor output shaft. The drive components are releasably secured together to facilitate unskilled disassembly for repair.

United States Patent 1 Bricker et al. g

in] 3,759,129 [4 1 Sept. 18, 1973 POWER UNIT [75] Inventors: Melvin E.Bricker; Thomas E. Dugle,

both of Cincinnati, Ohio [73] Assignee: Bricker Products, Inc.,Cincinnati,

Ohio

[22] Filed: May 4, 1972 [21] Appl. No.: 250,211

[52] US. Cl 83/444, 83/592, 83/571, 83/698, 308/184 [51] Int. Cl 826d7/26, 826d 4/22 [58] Field of Search 83/444, 698, 355, 83/356, 594, 571,591, 481, 592; 308/184 R [56] References Cited UNITED STATES PATENTS2,857,974 10/1958 Heller 308/184RX 3,066,714 12/1962 Qualheim 83/592FOREIGN PATENTS OR APPLICATIONS 805,085 11/1958 Great Britain 83/355Primary ExaminerWillie G. Abercrombie Attorney-James S. l-light et al.

[57] ABSTRACT An improved power unit for driving vegetable cuttingattachments comprises a housing, a motor mounted within the housing, anattachment supporting hub mounted on the front of the housing and adrive for connecting the motor to a shaft extension of the attachment.The drive includes a drive sleeve mounted'for rotation and radialdisplacement in the hub, a sprocket attached to the rear of the sleeveand a resilient bracket for universally and rotatably supporting therear end of the sleeve. The shaft extension of the vegetable cutterextends a relatively short distance into the front end of the drivesleeve to provide, in combination with the radial displacement of thesleeve and with the resilient rear bracket, a universal drivingconnection therebetween. A tensioner is provided to tension a chainconnecting the sprocket attached to the sleeve and a sprocket on a motoroutput shaft. The drive components are releasably secured togetherto-facilitate unskilled disassembly for repair.

12 Claims, 5 Drawing Figures rowan UNIT The invention relates generallyto power units for food cutters and is particularly directed to ahigh-speed drive for vegetable cutters, such as cabbage shredders,utilized in restaurants, carryout food stores and other establishmentswhich prepare food in large quantities.

A power unit somewhat similar to that of the present invention isdisclosed in my earlier U.S. Pat. No. 3,563,290. While this prior unithas proven to be efficient for driving various food processingattachments such as the one shown in my earlier US. Pat. No. 3,416,583,the power unit of the present invention provides an improved driveapparatus for transferring power from a motor to the drive shaft of theappropriate food processing attachment.

One problem with prior power units is that of alignment between thedrive shaft of the cutter attachment and the driving element of thepower unit. Where the drive shaft and driving element are rigidly heldin their respective units, and the connecting surfaces of the typicalconnecting hub of the power unit and the sleeve housing of the cutterare not made and assembled to rigid specifications, alignment of theshaft and driving element may present assembly and operating problemsincluding binding between the components involved. It can be appreciatedthat this alignment becomes severely critical when the drive element ofthe power unit is extended to the rear of the housing and is journalledboth at the front and the rear of the housing.

When some repair or adjustment. has been necessary to the drive of theprior power unit, it has generally been necessary to gain access to thefront portion of the housing, where various elements of the drive werelocated, from the rear of the unit. Not only was this awkward, but insome cases resulted in requiring skilled help to repair breakdown ormalfunctions. thereby increasing down time while the device wasinoperative. When a chain drive was utilized in the power unit, itresulted frequently in increased noise and vibrations.

One objective of the invention has been to provide a power unit with animproved drive which is simply and inexpensively manufactured and yetwhich operates with a minimum of noise and vibration, is easilydismantled forrepair by unskilled persons, and is selfaligning tofacilitate re-assembly and operation.

The present invention contemplates a relatively small, integral powerunit complete with a motor, an improved speed reducing drive apparatus,a hub for supporting a vegatable cutter attachment and apparatusestablishing a universal driving connection to the drive shaft extensionof a rotary cutter disc thereof. To this end,,the speed reducing driveincludes a sprocket mounted on a rearwardly extending motor shaft. Adrive sleeve is rotatably mounted between the front hub and a resilientrear mounting bracket and a driven sprocket is secured to a shaft,releasably held within the rear end of the drive sleeve. The shaft isjournalled in the rear bracket which provides a resilient mount on thepower unit to'enhance the smoothness and quietness of the operation andto provide for universal movement of the rear end of the device sleeveto further effect a universal connection as will be described. A chainis positioned between the motor sprocket and the driven sprocket toimpart rotational force thereto.

The drive sleeve extends through the front portion of the housing andthrough a bore in the hub, the bore being slightly larger than thesleeve and a flange provided about the sleeve. A resilient ring isprovided between the walls of the bore and the sleeve to allow the endof the sleeve to be radially displaced. An extension of the cutter driveshaft extends a short distance into the sleeve when a vegetable cutteror the like is mounted on the power unit, in order to transfer motionfrom the drive sleeve to the cutter plate, for example. The combinationof the radially displaceable end of the drive sleeve and the shortengagement of the shaft extension within the sleeve together with theuniversally mounted rear end of the sleeve results in a universalconnection between the sleeve and the extension.

A chain tensioner comprises a sprocket rotatably mounted on a leafspring which is releasably held be tween supporting surfaces on theresilient rear mounting bracket. When in operative position, thetensioner serves to impart a tensioning force on the chain. The tensioermay be easily manipulated out of operative position so that the chainand, in addition, all the drive components, may be easily removed forreplacement, adjustment, or repair.

One advantage of my improved power unit is that it can be simply andinexpensively constructed of relatively few parts and can be readilydisassembled for reapir by unskilled persons so as to minimize down timein the field.

Another highly important advantage of my improved power unit is that iteffects a universal driving connection between the driving components ofthe unit and the drive shaft extension of the food processingattachments connected thereto so as to accommodate axial misalignmenttherebetween and to facilitate reassembly and operation.

A further advantage of my improved power unit is that is operates with aminimum of noise and vibration.

These and other objects and advantages of the invention will be betterubderstood from a description of a preferred embodiment and from thedrawings, in which:

FIG. 1 is a general view of the power unit showing an attached vegetablecutter, a drive sleeve, and the connection between the drive sleeve andthe attached cutter,

FIG. 1A is an enlarged fragmentary view of the encircled area of FIG. 1,

FIG. 2 is a rear view showing the chain tensioner, the drive sleevesprocket, and the rear mounting bracket,

FIG. 3 is a view taken along lines 3-3 of FIG. 2 showing the details ofconnection between the drive sleeve, its sprocket and the rear mountingbracket, and

FIG. 4 is a view of the rear monting bracket and the supporting surfacesfor the chain tensioner.

Referring to FIGS. 1 and 1A, the power unit of my invention is indicatedat 10. It includes a housing 11, a hub 12 mounted on the forward portionof the housing 11, a motor l3, and a speed reducing drive 14 as will bedescribed. A vegetable cutter attachment 15 is shown attached to hub 12of the unit 10. One form of such attachment is shown in my previous U.S.Pat. No. 3,416,583. An attachment sleeve 16 extends from the cutter 15into the hub 12 and is locked in position by a wing screw of bolt 17. Acutter supporting and rotation shaft with a square extension 18 isrotatably supported in the attachment sleeve 16 for transmitting rotarymotion to a cutter head or plate l9.One typical form of cutterparticularly useful for shredding cabbage and the like is shown in mycopending application Ser. No. 875,805, filed Nov. 12, 1969, for aShredder Plate". The comminuted material, for example shredded cabbage,is discharged from the cutter attachment through a discharge chute 21.The driven shaft extension 18 has a chamfered end to ease its insertioninto a driving element of the power unit comprising a drive sleeve 22and the extension 18 extends into the sleeve 22 a distance approximatelyequal to the width of the square side of the shaft extension itself. Thehub 12 and the sleeve 22 may be provided in different sizes to ac cept avariety of vegetable cutters of different makes and attachments fordifferent functions.

The hub 12 is secured to a front wall 23 of the power unit housing 1 lby way of bolts 24. The hub 12 includes an inwardly extending annularflange 25 which cooperates indirectly with a circular flange 26 providedon drive sleeve 22 to inhibit motion of the drive sleeve 22 in arearward direction. The drive sleeve 22 extends in a generally rearwarddirection toward a rear mounting bracket 27. I

It will be noted that the bore defined by inwardly extending flange 25of the hub 12 is larger than drive sleeve 22 and that a bore 28 of thehub is larger than flange 26. Supporting the sleeve 22 for rotation inthe bore 28 is a self-lubricating ring 29 and a rubber washer 31surrounding and placed on ring 29. The outer surface of washer 31engages the bore 28 of the hub 12 while the inner surface ofself-lubricating ring 29 engages the drive sleeve 22. The resilience ofthe washer 31 allows the forward end of drive sleeve 22 to be radiallydisplaced to some degree and yet supports the sleeve for rotation withinthe hub. when a vegetable cutter or the like is connected to the hub 12,the drive sleeve may be radially positioned to align with the drivenshaft extension 18 of the cutter. Since washer 31 is resilient, thesleeve is aligned throughout the operation of the unit as can beappreciated.

The relatively short extension of shaft 18 into the sleeve 22 aspreviously stated, and the chamfered end of the extension 18 togetherwith the radial displacing feature of the forward end of the drivesleeve and with the to be described universal rear mount of the drivesleeve results in a universal type connection between the drive sleeve22 and the driven shaft extension 18. This universal connection negatesthe necessity of close manufacturing tolerances with respect to the hub12, the drive sleeve 22, and the connecting surfaces of the cutter 15.

The rear mounting bracket 27 includes a first or front plate 32 and asecond or rear plate 33. A resilient composition 34 such as rubber orany suitable compound is adhered by any suitable adhesive to plates 32and 33 so as to resiliently bind them together. The plate 32 has a bentor hook portion 35 which is shaped to support the bracket 27 over abracket or supportv 36 of the housing 11. A bolt 38 extends through abottom portion of the plate 32 to secure it to the bracket 27.

The support bracket 36 is welded or otherwise attached to the bottom ofhousing 11 and may have a reinforcing flange 37 also welded to thehousing at its bottom. The other side of the support bracket 36 is notwelded to the housing, and consequently the bracket itself is slightlyyieldable to allow some movement of bracket 27, should it be necessaryfor assembly or alignment of the drive.

A bracket 44 is located within drive sleeve 22 and is secured againstaxial movement by the cooperation of a button or deformed portion 45 onthe bracket and hold 46 in the sleeve 22. The bracket 44 has a dependingear of flange member 46 which is threaded to coop erate with bolt 48.This bolt has its head located on a seat 49 of the bore 42 and extendsthrough the shaft 41 to ear 47 of bracket 44 in order to secure theshaft 41 to the sleeve 22.

in this manner, the sprocket is releasably secured to the drive sleeve22 and it can be appreciated that, if bolt 48 is withdrawn from ear 47,the sprocket shaft 41 may be pulled from sleeve 22 and sleeve 22 may beremoved from the unit 10 by pushing it forwardly of the hub 12.

The sprocket shaft 41 is journalled for rotation in a bearing 51 mountedin a bore through plate 33 of the rear mounting bracket by means of asnap-ring 52. A clip 53 is bolted by bolt 54 to hold the bearing 51 inplace. The inner race of bearing 51 is ecurely held between the end 55of sleeve 22 and the annular seat 56 on the sprocket shaft 41.

Since the sprocket shaft 41 is journalled in the rear plate 33 and sincethe plate 33 is only resiliently secured to the front plate 32, theshaft 41 and the associated sprocket 39 are cushioned by the resilientcomposition 34. Such a mounting results in a universal support for therear end of the drive sleeve and shaft assembly. In addition theresilient bracket substantially reduces oeprating noise and vibration.Also, since the side of the support bracket 36 is not welded to thehousing of the power unit, no vibrations are transferred to this portionof the housing and any stress placed on the support 36 will not tend todeform the side of the housing but will be borne by the bottom portionof the housing which is stronger due to an adjacent bend at 57.

It should be noted that, while the preferred embodiment discloses thedetails of the sprocket 39 and driving shaft 41, the apparatus may beconstructed by extending sleeve 22 through the rear bracket 29 and anappropriate bearing and by securing the sprocket 39 directly to thesleeve near its rear end. Due to the resilience of bracket 27, the rearend of sleeve 22 would still be universally mounted.

The motor 13 is mounted within housing 11 by any suitable means such asby resilient mounts 58. The motor has a rearwardly extending output ordrive shaft 59 on which is connected a second rotatable means or motorsprocket 61. A flexible connecting means such as a chain 62 ispositioned about the sprockets 39 and 61 for transferring rotary motionfrom the motor sprocket 61 to sprocket 39. A belt and pulleys or anyflexible means connecting associated rotatable means may be used toconnect the motor to the drive sleeve, in place of the chain adsprockets described.

It will be noted that an end 63 of bent portion 35 of the bracket plate32 engages the top of side flange 37 of bracket support 36 so as tolimit lateral movement of the bracket 27 in a direction toward the motor13 when a load is transferred to the bracket by the chain 62. Thecombination of this engagement with the bolt 38 maintains the bracket 27against lateral movement (other than that allowed by resilientcomposition 34),

yet the bracket 27 is readily removed merely by the unthreading of bolt38 and by an upwardly motion to clear the bent portion 35 from thebracket 36.

A chain tensioner 64 is generally shown in FIG. 2 and its support inFIGS. 3 and 4. The tensioner comprises a sprocket 65 rotatably mountedon a leaf spring 66. The spring 66 is pre-shaped such that it urges thesprocket 65 in a downwardly direction when it is held in correctoperative position.

The spring 66 is releasably mounted on plate 33 of bracket 27bysupporting surfaces including an upper flange 67 and a lower flange68. The lower flange 68 has a hole 69 which is shaped to receive a lug71 provided on the leaf spring.

When the tensioner 64 is in operative position, the sprocket 65 ispositioned on the chain 62, and the leaf 66 is stressed upwardly againstits supporting flange 67, and downwardly against its supporting flange68 so that the lug 71 is held in the hole 69 and such that the tensioner64 is secured against any undesired movement. Since the leaf 66 of thetensioner is mounted on the cushioned plate 33, its vibrations and noiseare substantially reduced as are the vibrations from sprocket shaft 41.

For removing the chain 62, the leaf 66 may be lifted against its bias byhand, and the chain removed from the sprockets 39 and 61. The leaf 66may then be moved downwardly and removed from the'unit 10, as can beappreciated. To install a new chain it is ony necessary that the leaf 66be inserted between the flanges 67 and 68 and raised against its bias sothat a chain 62 may be fitted about the sprockets. The sprocket 65 isthen lowered onto the chain to tension it. Starting and stoppingstresses on the chain 62 are somewhat re lieved by the resilientmounting of the motor and of the sprocket 39 and by the slightlyyieldable nature of the bracket 27.

If it is desired to disassemble the complete drive, once the chain' andtensioner are removed, the bolt 48 may be removed and then sprocket 39with the sprocket shaft 41 can be removed in a rearward direction. Thedrive sleeve.22 is then removed forwardly through the hub 12. Bolt 38 isremoved and the rear bracket 27 lifted from the support bracket 36.Bolts 38, 48' and 54 may have thesame Allen-head sizeso as to requireonly one wrench for removal thereof and to facilitate take-down.Reassembly of the drive is self evident and is facilitated by the natureof the resilient fit of the front end of the drive sleeve 22 in the hub12 and by the slightly yieldable rear support bracket 26 as well as theresilient connection betwee the front and rear plates 32 and 33 of thebracket 27.

The housing 11 is supported by two rear legs 72 and by two front legs73. The legs are welded to bottom members 74, the front legs beingwelded'perpendicular to the bottom members 74 and then bent to the angleshown so as to eliminate any pockets about the joint which are difficultto clean. Legs 75 are provided within the members 74 and may be extendedor retracted in the direction of arrow A" for storage. Extension of thelegs 75 increases the stability of the unit as well as provides supportsfor a food receiving tray (not shown) to be placed beneath the chute 21of vegetable cutter attachment 15. The legs 75 have pads 76 on the endsthereof for supporting the ends of the legs or for providing stops for atray placed on the legs beneath the chute 21 through which processedfood is discharged.

It will be noted that the two front legs 73 support the front of thehousing 11 at a greater height with respect to the horizontal than theback portion of the housing in the manner shown in my previous U.S. Pat.No. 3,563,290. This has the effect of elevating the drive axis of thehub 12 and drive sleeve 22 at an appreciable angle, for example of from15 to 20. This construction has the advantage of increased stability, itfacilitates the gravity feed of the vegetable cuter thereby reducingoperating time and elevates the cutter above the units supportingsurface to provide a convenient space for the insertion of a foodreceiving container beneath the cutters discharge chute.

It can be readily appreciated that the disclosed power unit is veryserviceable and efficient, and has substantial reductions in noise andvibrations. The components are very easily and inexpensivelymanufactured and require no precise fitting or machinery, yet they areselfaligning to produce a very efficient and positive drive.

Furthermore, it can be appreciated that the components may be completelydisassembled or assembled by one of relatively little skill in the artfor the purpose of repair and replacement. This decreases machine downtime since spare parts may be kept on hand and immediately placed intouse to replace defective or worn parts.

The placement of the elements of the drive in the rear of the unit 10greatly aids in ready access to them and enables the housing to beattractively made as an integral piece with only a removable or hingedback panel.

The power unit of the present invention incorporates all the advantagesof the previous unit shown in my earlier U.S. Pat. No. 3,563,290.

While I have described my invention in detail, other modifications andadvantages will become readily apparent to those of ordinary skill inthe art and I intend to be bound only by the appended claims.

I claim:

1. A power unit for driving a vegetable cutter attachment having ahopper, a high speed cutter, a drive shaft for supporting and rotatingthe cutter and including a shaft extension for connection to the powerunit, said power unit comprising:

a housing a motor mounted within said housing and including an outputshaft;

an attachment supporting hub mounted on the housrng,

an elongated drive sleeve adapted for connection to said shaft extensionat said hub and extending rearwardly from said hub,

means for effecting a universal driving connection between said drivesleeve and said shaft extension to accommodate axial misalignmentbetween said sleeve and said extension, said means including meansrotatably and universally mounting said sleeve near its rear end and inproximity to a rear portion of the housing and means supporting saidsleeve in said hub for rotational and radial motion, and

means for connecting said motor output shaft to said drive sleeve toeffect a driving connection between said output shaft and said sleeve.

2. A power unit as in claim 1 wherein said universal connection furtherincludes a relatively short engagement between said drive sleeve andsaid shaft extension.

3. A power unit as in claim 2 wherein an end of said attachment driveshaft extension is generally square in cross section and is chamferedand wherein it extends into and engages said drive sleeve a distanceapproximately equal to the width of its square cross section so as toeffect the universal connection between said drive sleeve and saidattachment drive shaft.

4. A power unit as in claim 1 wherein said means rotatably and pivotallymounting said drive sleeve includes a support and a rear mountingbracket which comprises:

a first plate,

means for relasably attaching said first plate to the support,

a second plate provided with a bearing means for supporting said sleevefor rotation, and

resilient means adhered to the first and second plates to resilientlyconnect said plates together.

5. A power unit as in claim 1 wheein said means for connecting the motoroutput shaft to the drive sleeve includes a first rotatable meanssecured to said drive sleeve near its rear end, a second rotatable meanssecured to the output shaft of said motor, and flexible meansoperatively connecting said first and second rotatable means.

6. A power unit as in claim 5 wherein said first rotatable means isoperatively mounted on a driving shaft journalled in a rear mountingbracket and wherein said driving shaft extends forwardly of said bracketand into said drive sleeve, said driving shaft cooperating with saiddrive sleeve to support it and impart rotary motion thereto.

7. A power unit as in claim 6 wherein a fastening means extends throughsaid driving shaft and into a non-yielding member in said sleeve forreleasably securing said first rotatable means and said driving shaft tosaid sleeve.

8. A power unit as in claim 6 wherein said rear mounting bracketcomprises:

a first plate with a flanged top portion for cooperation with a support,

fastening means in a lower portion of said first plate for attaching thefirst plate and the support together,

a second plate provided with a bore for the driving shaft, and

a resilient means positioned between said first and second plates andadhered thereto for resiliently securing said plates together.

9. A power unit as in claim 5 wherein a tensioning means is positionedto tension said flexible means and wherein said tensioning meansinclude:

a third rotatable means for directly engaging said flexible means, saidthird rotatable means being mounted on a leaf spring, and

said leaf spring being releasably held by cooperating surfaces on amounting bracket.

10. A power unit as in claim 9 wherein said mounting bracket includes afirst plate releasably secured to a support, and a second plateresiliently secured to the first plate, said cooperating surfaces beinglocated on said second plate and including upper and lower flange meansfor releasably supporting said leaf spring in a position to urge saidrotatable means into tensioning contact with said flexible means.

11. A power unit as in claim 9 wherein said first, second and thirdrotatable means comprise sprockets, and wherein said flexible means is achain.

12. A power unit as in claim 1 including means supporting said housingat an angle relative to the horizontal with a front wall of the housingbeing elevated.

1. A power unit for driving a vegetable cutter attachment having ahopper, a high speed cutter, a drive shaft for supporting and rotatingthe cutter and including a shaft extension for connection to the powerunit, said power unit comprising: a housing a motor mounted within saidhousing and including an output shaft; an attachment supporting hubmounted on the housing, an elongated drive sleeve adapted for connectionto said shaft extension at said hub and extending rearwardly from saidhub, means for effecting a universal driving connection between saiddrive sleeve and said shaft extension to accommodate axial misalignmentbetween said sleeve and said extension, said means including meansrotatably and universally mounting said sleeve near its rear end and inproximity to a rear portion of the housing and means supporting saidsleeve in said hub for rotational and radial motion, and means forconnecting said motor output shaft to said drive sleeve to effect adriving connection between said output shaft and said sleeve.
 2. A powerunit as in claim 1 wherein said universal connection further includes arelatively short engagement between said drive sleeve and said shaftextension.
 3. A power unit as in claim 2 wherein an end of saidattachment drive shaft extension is generally square in cross sectionand is chamfered and wherein it extends into and engages said drivesleeve a distance approximately equal to the width of its square crosssection so as to effect the universal connection between said drivesleeve and said attachment drive shaft.
 4. A power unit as in claim 1wherein said means rotatably and pivotally mounting said drive sleeveincludes a support and a rear mounting bracket which comprises: a firstplate, means for relasably attaching said first plate to the support, asecond plate provided with a bearing means for supporting said sleevefor rotation, and resilient means adhered to the first and second platesto resiliently connect said plates together.
 5. A power unit as in claim1 wheein said means for connecting the motor output shaft to the drivesleeve includes a first rotatable means secured to said drive sleevenear its rear end, a second rotatable means secured to the output shaftof said motor, and flexible means operatively connecting said first andsecond rotatable means.
 6. A power unit as in claim 5 wherein said firstrotatable means is operatively mounted on a driving shaft journalled ina rear mounting bracket and wherein said driving shaft extends forwardlyof said bracket and into said drive sleeve, said driving shaftcooperating with said drive sleeve to support it and impart rotarymotion thereto.
 7. A power unit as in claim 6 wherein a fastening meansextends through said driving shaft and into a non-yielding member insaid sleeve for releasably securing said first rotatable means and saiddriving shaft to said sleeve.
 8. A power unit as in claim 6 wherein saidrear mounting bracket comprises: a first plate with a flanged topPortion for cooperation with a support, fastening means in a lowerportion of said first plate for attaching the first plate and thesupport together, a second plate provided with a bore for the drivingshaft, and a resilient means positioned between said first and secondplates and adhered thereto for resiliently securing said platestogether.
 9. A power unit as in claim 5 wherein a tensioning means ispositioned to tension said flexible means and wherein said tensioningmeans include: a third rotatable means for directly engaging saidflexible means, said third rotatable means being mounted on a leafspring, and said leaf spring being releasably held by cooperatingsurfaces on a mounting bracket.
 10. A power unit as in claim 9 whereinsaid mounting bracket includes a first plate releasably secured to asupport, and a second plate resiliently secured to the first plate, saidcooperating surfaces being located on said second plate and includingupper and lower flange means for releasably supporting said leaf springin a position to urge said rotatable means into tensioning contact withsaid flexible means.
 11. A power unit as in claim 9 wherein said first,second and third rotatable means comprise sprockets, and wherein saidflexible means is a chain.
 12. A power unit as in claim 1 includingmeans supporting said housing at an angle relative to the horizontalwith a front wall of the housing being elevated.